Colin, sorry, I have no idea what caused the error but there always seems to be work arounds to enable one to leave home with some (but not total faith).
It took me a lot of trials and new problems before I could feel safe(ish), I do trading mainly so have to protect against lots of things, mainly surrounding bets not being hedged at the start of the race.
I place bets with one platform, then in case that is too busy at the start I use a second platform monitoring less martkets to do the greening up.
Then I run the same green up platform on another laptop a few seconds later in case the first laptop crashes.
I used to use a desktop but now I uses two laptops as they have the battery to back up if the mains fails - but I have to hope the modem/router restarts when the mains power comes back. I am thinking about getting a UPS for them.
I have a trigger that deletes bets if there is more than one unmatched bet on a selection to assist when the "number of matched bets" condition not being checked properly due to connection speed, as sometimes happens.
I make sure that the bank cannot go below a level to leave enough cash to green up.
I delete unmatched bets if price has moved away and left a bet stranded away from the market.
Also other things I have put in but cannot even remember.
I still am left exposed if the internet goes down (all my attempts to get a VPS failed as Betfair always said it was outside UK when it wasn't). That happened last Friday and I was lucky as three well priced backs went of unhedged - and won quite a bit! (It sometimes goes the other way though)
If Betfair API goes down I am also knackered!! (Thankfully less than it used to - fingers crossed).
You can use a trigger to delete unmatched bets, or unmatched bets at 1000, or other things! (Better to solve the problem though if anyone can help).